The long-term goal of our research is to understand the cortical mechanisms that limit vision development in primates. Normal infants and amblyopic adults perform poorly in global perceptual tasks. The primary goal of this proposal is to examine the hypothesis that the immature/subnormal receptive-field (RF) structures of neurons in the earliest stages of extrastriate processing (V2 and V3), in particular, the inability of these neurons to precisely pool local feature information over space, impose significant limits on the development of the perceptual decision-making mechanisms downstream. With our microelectrode recording methods, we will study the receptive-field center and surround structures of V2 and V3 neurons of macaque monkeys (Macaca mulatta) at key developmental ages, and we will ask how experiencing binocularly discordant images early in life alters the RF structures of these extrastriate neurons. To reveal the RF center and surround structure of each neuron, we will quantitatively analyze the spatial organization (geometric map) of 'subfields'(local sensitivities) within the RF center and the 'sub-regions'of the RF surround. We will also study the nature (i.e., facilitatory or suppressive) and the strength of signal interactions between subfields within the RF center, and between the RF center and surround sub-regions. To explore a link between immature extrastriate cortical physiology of infants and anomalous visual processing in amblyopic adults, we will examine the hypothesis that robust binocular suppression, highly prevalent in the striate visual cortex (V1) of strabismic monkeys during early infancy, arrests and/or disrupts the normal development of neuronal circuits underlying the RF structures of V2 and V3 neurons of amblyopic monkeys. The proposed research will provide a better understanding of how neuronal processing in one cortical area can influence neural events in other areas. More importantly, we will gain insights into how such complex striate/extrastriate interactions mature under normal and abnormal visual environments.

Public Health Relevance

Amblyopia ('lazy eye') is a developmental vision disorder. This investigation proposes to explore the neuronal mechanisms in the primate visual brain that limit visual performance of amblyopic adults and normal infants using electrophysiological and behavioral methods. The primary goal is to establish a link between immature cortical physiology in normal infants and abnormal visual processing in amblyopic patients. The proposed research will generate the information that will have a significant impact on the development of effective strategies for the prevention and treatment of vision disorders.